Pulse frequency modulator



May 31, 1955 E. D. sco'rr 2,709,803

PULSE FREQUENCY MODULATOR Filed Aug. 1, 1947 TO MOTOR CONTROL 42 40 Qwucmto o EARL D. SCOTT Maw/1 2,7ti9,8il3

PULSE FREQUENCY MODULATOR Earl D. Scott, Portland, Greg. Application August 1, 1947, Serial No. 765,618 7 Claims. (Cl. Mil-353) (Granted under Title 35, U. 5. Code (1952), see. 266) This invention relates to electrical impulse generators and more particularly to a mechanical device for generating electrical impulses having predetermined rep etition frequency variation characteristics.

The necessity of employing an impulse generator capable of producing electrical impulses having selectable, repetition frequency variation characteristics in connection with numerous applications of electrical equipment is fully appreciated by those skilled in the art. To produce a series of electrical impulses having the foregoing characteristics with electronic means, an extremely complex device, including a multiplicity of electron tubes, is required.

It is therefore an object of the present invention to provide mechanical means for generating electrical impulses having predetermined repetition frequency variation characteristics.

Another object is to provide mechanical means for generating electrical impulses having predetermined repetition frequency variation characteristics including means selectively varying such predetermined repetition frequency variation.

Other objects and features of the present invention will appear more fully hereinafter from the following detailed description when considered in connection with the accompanying drawing which discloses one embodiment of the invention. It is to be expressly understood however, that the drawing is designed for purposes of illustration only and is not to be considered as a definition of the limits of the invention, reference to the latter purpose being had to the appended claims.

in the drawing, wherein similar reference characters denote similar elements throughout the several views:

Fig. 1 is a diagrammatic plan view of a mechanical impulse generator constructed in accordance with the principles of the present invention, and

Fig. 2 is a cross-sectional view taken on the line 2-2 of Fig. 1.

With reference more particularly to the drawing, a mechanical impulse generator embodying the principles of the present invention is disclosed therein including a rectangular base member 10, constructed of any suitable material, having the opposite edges thereof terminating in portions 11 and 12 of uniformly increased thickness. Each of the portions 11 and 12 respectively include longitudinal lips 13 and 14 extending inwardly therefrom, with respect to the edges of the member 10, in spaced relation from the surface of the member 1%, to define a pair of parallel channels, of rectangular cross-section, extending throughout the entire length of the member 1%) at opposite sides thereof. A carriage 15, constructed of insulating material, is slidably mounted on the face of the member 10. A pair of diametrically opposed edges of the carriage 15 extend into the channels defined by longitudinal lips 13 and 14 to allow only relative longitudinal movement between the carriage 15 and the member 10. For a purpose that will appear more fully hereinafter, means are provided States Patent Gfice Patented May 31, 1955 for controlling the relative longitudinal movement between the carriage 15 and the member 16. Such control means includes a rack 16 mounted on the surface of the carriage 15 parallel and adjacent to the longitudinal lip 13, and a pinion 17 supported on the lip 13 in meshing engagement with the rack 16 by means of a shaft 18 and a bearing support 19. The rack 16 and pinion 17 is operated by a thumb wheel 20 to impart relative movement between the carriage 15 and the member 10.

As shown in the drawing, the mechanical impulse generator further includes a circular potential distributor symmetrically mounted on the surface of the carriage 15. The circular potential distributor includes a plurality of sectors, 21, 22, 23, 24, 25, 26, 27, and 28, constructed of conductive material. Each of the sectors are insulated from adjacent sectors by a plurality of spacers 29, constructed of high resistance material, which terminate at a common point 39. The electrical circuit to the circular potential distributor includes terminals 31 and 32, shunted by a suitable resistance 33. Terminal 31 is connected through circular conductor 34 to conductive sectors 22, 24, 26, and 28, while terminal 32 is connected through a source of potential, such as battery 35, and through circular conductor 36 to conductive sectors 21, 23, 25, and 27.

In order to produce a train of electrical impulses, at terminals 31 and 32, with the duration of the time spacing between successive impulses varying in a predetermined manner, means are provided for successively forming an electrical contact between adjacent conductive sectors of conductive sectors 21, 22, 23, 24, 25, 26, 27, and 28, with the time between successive electrical contacts varying in such predetermined manner. The foregoing means, as shown in the drawing, includes a contact arm 37 having one end thereof secured to a shaft 38. The other end of the contact arm 37 includes contact 39, constructed of conductive material, having a width greater than the width of spacers 29. The shaft 38 is mounted for rotation about an axis perpendicular to the carriage 15 by a suitable bearing support in a supporting member 4%. As shown in Pig. 2, the supporting member 49 includes end members 41 and 42 which extend downwardly at opposite ends thereof and terminate in rigid relationship with the portions 11 and 12 respectively, to rigidly support the member 40 in spaced relation with the carriage 15. A motor 43 is mounted on member 40 and operatively connected to the upper end of the shaft 38, to impart rotation to the shaft 38 and to thereby rotate the contact 39 about the axis of the shaft 33. The motor 43 is controlled through a suitable motor control device, not shown, to selectively apply constant speeds of rotation to the shaft 38.

With the foregoing arrangement, when the pinion 17 and rack 16 is operated through rotation of the thumb wheel 20 to adjust the relative position between the carriage 15 and the member 16 so that the axis of rotation of the shaft 38 coincides with the point 39, and when motor 43 is controlled to rotate the shaft 38 at a predetermined constant speed, the contact 39 will move at constant angular velocity, requiring equal periods of time to traverse each of the conductive sectors 21, 22, 23, 24, 25, 26, 27, and 28 throughout each complete revolution of the shaft 38. Since the contact 39 Suecessively established contact between adjacent conductive sectors at equal instances a train of electrical impulses appears at the terminals 31 and 32 having a constant repetition frequency, that is, the duration of the time intervals between successive electrical impulses remains constant. The duration of the electrical impulses and the time interval between successive impulses is readily varied by varying the constant speed of rotation ofthe shaft 32.

When it is desired to produce a train of electrical impulses having predetermined repetition frequency variation characteristics, the carriage 15 is moved relative to the member 10, through rotation of the thumb wheel 20, to off-set the axis of rotation of the shaft 33 from the point 3%, as shown in Fig. 1. The motor 43. is operated to impart a predetermined constant speed of rotation to the shaft 33 to thereby rotate the contact 39 at a constant angular velocity. Since the center of the circular path described by the rotating contact 39 is displaced from the point 39, the time intervals be.- tween successive establishments of contact between adjacent conductive sectors varies throughout each complete revolution of the contact 39. Therefore, the pulse repetition frequency of the electrical impulses appearing at the terminals 31 and 52 is frequency modulated at the rotational frequency of the shaft 38. The degree of frequency modulation is directly proportional to the degree of displacement between the axis of the shaft 38 and the point 3%.

There is thus provided by the present invention amechanical impulse generator for producing a train of electrical impulses having predetermined repetition fre- 4 quency variation characteristics. In particular, the generator includes means whereby the duration of the time interval between successive impulses of a series of impulses is modulated in a predetermined manner at a known frequency. Moreover, the generator is so characterized that the degree of such modulation and the known frequency are readily varied.

Although only one embodiment of the invention has been disclosed and described herein it is to be expressly understood that various changes and substitutions may be made therein without departing from the spirit of the invention, as well understood. by those skilled in the art. Reference therefore will be had to the appended claims for a definition of the limits of the invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor;

What is claimed is:

1. A mechanical impulse generator comprising a plurality of conductors, a plurality of spacers insulating each of said conductors from the remainder of said conductors, a load circuit connected between adjacent conductors of said conductors and means successively establishing electrical contact between said adjacent conductors in accordance with a predetermined function.

2. A mechanical impulse generator comprising a plurality of conductors, a plurality of spacers insulating each of said conductors from the remainder of said conductors, a source of potential, a load circuit, means serially connecting said source and said load between adjacent conductors of said conductors, means successively establishing electrical contact between said adjacent conductors in accordance with a predetermined function and. means varying said function.

3. An impulse generator comprising a plurality of conductor sectors, a plurality of spacers intersecting at a common point insulating each of said conductor sectors from the remainder of said conductor sectors, circuit means electrically connected between adjacent sectors of said conductor sectors, a rotating member mounted to successively establish electrical contact be tween adjacent sectors and means displacing the axis of rotation of said member from said point.

4. An impulse generator comprising a supporting member, a carriage member adiustably positioned on said supporting member, a plurality of conductor sectors mounted on said carriage member, means insulat ing each of said conductor sectors from the remaining conductor sectors, said insulating means including a plurality of insulating spacers positioned between adjacent conductor sectors and intersecting at a common point, circuit means electrically connected to adjacent sectors of said conductor sectors, a shunting member mounted in fixed position with respect to said supporting member and rotatable to successively bridge said spaces between adjacent conductor sectors and means adjusting the relative position of said carriage member With respect to said supporting member to displace the center of rotation of said shunting member from said point.

5. A mechanical impulse generator comprising a plurality of conductor sectors, a plurality of spacers intersecting at a common point insulating each of said conductor sectors from the remainder of said conductor sectors, a source of potential and a load circuit connected serially between adjacent sectors of said conductor sectors and a contact member rotatably mounted with respect to said sectors to successively establish electrical contact between adjacent sectors.

6. A mechanical impulse generator comprising a plurality of conductor sectors, a plurality of spacers intersecting at a common point insulating each of said conductor sectors from the remainder of said conductor sectors, a source of potential and a load circuit connected serially between adjacent sectors of said conductor sectors, and a rotating contact member mounted to successively establish electrical contact between adjacent sectors, the axis of rotation of said contact memher being displaced from said common point to provide a series of electrical pulses having predetermined repetition frequency variations.

7. Adevice as described in claim 6 including means for displacing said axis of rotation.

References Cited in the file of this patent UNITED STATES FATENTS 1,l72,017 Fessenden Feb. 15, 1916 1,543,475 Lemmon June 23, 1925 1,893,019 Culver lan. 3, 1933 

